1. FIELD OF THE INVENTION
The present invention relates in general to jet pumps and, in particular, to jet pumps having a Venturi chamber with a high erosion resistant surface coating.
2. DESCRIPTION OF THE PRIOR ART
Jet pumps are well known. Typically, a power fluid under relatively high pressure passes through a nozzle and aspirates into its stream a fluid to be pumped, for example, production fluid from an oil well. The combined stream enters the throat of a Venturi and passes into a diffusion chamber of the Venturi where the high velocity streams recover a static pressure head.
Production fluids generally have an appreciable solid content. Most common of the solid content is sand, which is highly erosive. The Venturi of a jet pump has a comparatively small passage, the throat, through which the power and well fluid streams pass at high velocity. The erosive power of solids at these high velocities is substantial. A prior art solution to these problems has been to fabricate Venturi throats and diffusion chambers out of ceramic materials because these materials resist erosion.
The Venturi of a jet pump used in a down hole location is additionally subjected to considerable mechanical stress. The pressure of well fluid at the formation may be about a thousand PSI. Such fluid acting radially inward on a ceramic Venturi opposes a radially outward pressure within the Venturi which can achieve a level of about six thousand PSI, with the net result that the ceramic Venturi is loaded in tensile hoop stress to a considerable degree.
It is well known that ceramic materials do not posses significant tensile stress resistance, but they do have a much greater resistance to compressive force than to tensile forces. Hence, it is desirable to impose a preloaded compressive stress on the ceramic element of a Venturi.